Field of the Invention
The invention relates to a hearing assistance system, comprising a first hearing device to be worn at a first one of a user's ears, and a second hearing device to be worn at a second one of the user's ears, each hearing device comprising an interface for receiving an external audio data stream from an external audio source device with the hearing devices being adapted to establish a binaural data link between the first hearing device and the second hearing device.
Description of Related Art
Typically, the link from and to such external audio source device, such as a phone device or an audio streamer like a TV-set, is a BLUETOOTH® (BT) link which, being in the 2.4 GHz ISM band, may suffer from multipath effects, interference from other unrelated BT or Wi-Fi links and highly varying link margins, e.g., due to head shadow effects (electromagnetic radiation at 2.4 GHz can penetrate human tissue only a few centimetres before being fully absorbed). Thus, use situations like having, e.g., a smartphone in a pocket or handbag on one side of the body, or not facing a TV set or moving around (e.g., grabbing some beer in the kitchen while the TV is switched on) may create conditions, where one hearing device receives signals of sufficient strength whereas the other one does not. Moreover, when multiple TV sets are on (e.g., one in the living room, one in the kitchen, one in the children's room and one in the neighbor's living room right behind a wall), it can easily happen that one hearing device receives the strongest signal from one TV set, whereas the other one receives it from another TV set. As the hearing devices are not paired to the neighbor's TV set, they will not be able to receive that TV set's (encrypted) audio, but unconditionally connecting to the strongest source will lead to a strange and unpredictable behavior, as physical distance to a source does not necessarily correlate with the signal strength of strongest source as well (as it usually would be for acoustic sources). As a result, one of the two hearing device may lose the audio connection whereas the other does not even within a close proximity, or one hearing device suddenly switches to a different source while the other does not, so that each ear receives different audio content. Generally, such behaviors are undesirable.
Moreover, audio source devices like TV sets or smart phones can transmit with higher power than hearing devices and may have more efficient transmission systems (better antennae due to fewer physical volume constraints). This results in an asymmetrical link condition, where BT communication, e.g., from a smartphone to a hearing device is possible, while the hearing device is not able to communicate to the smartphone.
When a wireless audio sink, such as a wireless hearing device, loses connectivity to an audio source, it may be configured to automatically reconnect to the audio source in case the audio source is still in range and the link loss is only of temporary nature. Link loss can happen, for example, due to head shadowing effects or localized interference. The benefit of an automatic reconnect is that the end user operating the audio sink does not need to intervene. However, the automatic reconnect comes at a cost, namely scanning for the presence of an audio source is power and time consuming. Furthermore, if the audio source is out of range, i.e., the link loss is permanent, the audio sink may expend a lot of energy trying to reconnect automatically.
U.S. Pat. No. 8,300,864 B2 relates to a binaural hearing aid system, wherein an audio stream from a telephone device is transmitted via a short range inductive link to one of the hearing aids and is forwarded via a second wireless link which is used by the hearing aids to exchange data to the other hearing aid.
U.S. Pat. No. 8,041,066 B2 relates to a binaural hearing aid system, wherein one of the two stereo channels received by one of the hearing aids via a wireless link is forwarded to the other hearing aid via a wireless link.
Other examples wherein an audio stream received via a BT link from an audio source is relayed to the other ear are described in U.S. Pat. Nos. 8,706,038 B2, 9,002,044 B2, and 8,155,335 B2. Also U.S. Patent Application Publication 2007/0037615 A1 relates to a system wherein an audio source, such as a mobile phone, sends an audio signal via a BT link to a hearing device which forwards the audio signal via a binaural link to the other hearing device.
U.S. Pat. No. 8,768,252 B2 relates to system wherein a Bluetooth audio source is connected via a Bluetooth link to a first loudspeaker for transmitting an audio signal to the first loudspeaker, and wherein a wireless link between the first loudspeaker and a second loudspeaker is used for forwarding audio data received from the audio source to the second loudspeaker.
U.S. Patent Application Publication 2013/0108058 A1 relates to two hearing devices connected via binaural link, wherein the quality of the binaural link is monitored in order to adjust the operation mode of each haring device according to the quality of the binaural link.
U.S. Patent Application Publication 2012/0231732 A1 relates to a system wherein an audio source sends an audio signal to two binaural hearing devices, with the hearing device having the better RSSI sending a baseband audio signal via an NFC link to the other hearing device.
U.S. Patent Application Publication 2009/0197532 A1 relates to a pair of earphones, wherein in a first mode one of the earphone receives an audio stream via a BT link from a mobile phone and relays it via a different wireless link to the other earphone, and wherein in a second mode the roles of the earphones are interchanged; switching between the two modes occurs according to the battery levels of the earphones in order to achieve balanced battery drain.
U.S. Patent Application Publication 2011/0158441 A1 relates to similar system comprising a pair of BT earphones, wherein the wireless link connecting the earphones is a BT link like the BT link via which the audio stream from the mobile phone is received; the roles of the earphones are switched according to the respective battery levels.
U.S. Pat. No. 8,526,648 B2 relates to a binaural hearing assistance system, wherein an audio signal from a wireless microphone is transmitted to the hearing devices, wherein the link quality to each hearing device is monitored, and wherein the signal received via the better link is relayed via a binaural link to the other hearing device.
U.S. Pat. No. 8,050,439 B2 relates to a binaural hearing system, wherein a bidirectional wireless link between the two hearing aids is used to exchange information concerning the battery charge status of each hearing aid in order to reduce power consumption of the hearing aid having the lower remaining battery lifetime once the difference of the remaining battery charges exceeds a certain limit.
U.S. Pat. No. 8,712,083 B2 relates to data logging in a wireless hearing aid system in order to modify link parameters in a manner to enhance reliability and link quality.
International Patent Application Publication WO 2014/114818 A2 relates to a binaural hearing system, wherein the scanning activity for an audio source in a carrier detect mode is distributed onto the two hearing devices in a coordinated manner for saving power; once one of the hearing devices detects an audio source, it notifies the other hearing device accordingly.
U.S. Patent Application Publication 2012/0121095 A1 relates to a binaural hearing system, wherein the two hearing devices alternate to send beacons to a mobile phone in order to prevent the mobile phone connection from losing connection with the hearing devices.
International Patent Application Publication WO 2014/114819 A2 relates to a binaural hearing system wherein an external device, such as a mobile phone, which is anyway connected to the hearing device scans for audio sources and notifies the hearing device when it detects an audio source.
U.S. Patent Application Publication 2014/0193007 A1 relates to a hearing system with activation/deactivation of audio streaming to a hearing device depending on the sensed motion of the hearing device user.